1. Field of Endeavor
The present invention relates to gas turbines, and more specifically to an axial flow gas turbine
Yet more specifically, the invention relates to a stator heat shield protecting the vane carrier of an axial-flow turbine used in a gas turbine unit.
2. Brief Description of the Related Art
An example of an axial flow gas turbine is shown in FIG. 1. The gas turbine 10 of FIG. 1 operates according to the principle of sequential combustion. It includes a compressor 11, a first combustion chamber 14 with a plurality of burners 13 and a first fuel supply 12, a high-pressure turbine 15, a second combustion chamber 17 with the second fuel supply 16, and a low-pressure turbine 18 with alternating rows of blades 20 and vanes 21, which are arranged in a plurality of turbine stages arranged along the machine axis MA.
The gas turbine 10 according to FIG. 1 includes a stator and a rotor. The stator includes a vane carrier 19 with the vanes 21 mounted therein; these vanes 21 are necessary to form profiled channels where hot gas developed in the combustion chamber 17 flows through. Gas flowing through the hot gas path 22 in the required direction hits against the blades 20 installed in shaft slits of a rotor shaft and causes the turbine rotor to rotate. To protect the stator housing against the hot gas flowing above the blades 20, stator heat shields installed between adjacent vane rows are used. High temperature turbine stages require cooling air to be supplied into vanes, stator heat shields, and blades.
The stator heat shields are installed in gas turbine housings above blade rows. The stator heat shields preclude hot gas penetration into the cooling air cavity and form the outer surface of the turbine flow path 22. For the purposes of economy, sometimes a cooling air supply between a vane carrier and a stator heat shield is not used. However, in this case stator heat shields are also necessary to protect the vane carrier.